It is very common, especially in cities and municipalities, as well as in industrial settings, for various types of utilities to be routed underground, and accessed through manholes extending downward from, e.g., the surface of a street or other paved or unpaved area to the utility zone. Manholes, which are typically cylindrical shafts or enclosures are formed of a variety of materials such as brick or concrete, but are fairly uniformly capped by a mounting ring that fits onto the top of the manhole and a manhole cover that fits into the ring. Manhole covers are typically formed of metal, although other materials can be used, and are normally very substantial and heavy, so that they will withstand the weight of vehicles passing over them, and will discourage casual removal by unauthorized persons. However, the manhole covers must be removed whenever it is necessary to gain access to the manhole, and the size and weight of the covers can make this a difficult process.
Workers often encounter another problem with removal of manhole covers, in addition to their weight. It is common for manhole covers to become adhered to or jammed into the mounting rings, as a result of a variety of factors or combination of factors, including the weight of vehicles traveling over them, corrosion, dirt and debris, and the intrusion of paving materials between the cover and ring. In that situation, applying lifting force to the manhole cover itself can pull the ring away from the manhole structure along with the cover. When that occurs the cover must be refitted to the manhole, grouted in place, and, often, any paving around the cover must be repaired, which can be a time consuming and costly procedure.
Various types of devices and apparatus for lifting and moving manhole covers are known in the prior art, ranging from simple mechanical lever devices to complex vehicle mounted electromagnetic apparatus. Although the devices and apparatus of the prior art are reasonably effective in applying a lifting force for the manhole cover, the prior art has not effectively addressed the problem of lifting and removing a manhole cover without disturbing the mounting ring.